Melt stabilized polyketone blend containing a mixture of magnesium oxide and alumina

ABSTRACT

A stabilized polymer composition comprising a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, and a melt stabilizer comprising a mixture of magnesium oxide and alumina. A process of preparing the composition and articles of manufacture made of the composition are also disclosed.

FIELD OF THE INVENTION

This invention generally relates to polyketone polymers. Moreparticularly, this invention relates to a stabilized polyketone polymercomposition comprising the polymer and a melt stabilizing agent.

BACKGROUND OF THE INVENTION

Polymers of carbon monoxide and olefins generally referred to aspolyketones are well known in the art. Such polymers are disclosed in,for example U.S. Pat. Nos. 2,495,286; 3,694,412; and U.K. 1,081,304which are herein incorporated by reference.

Of particular interest among polyketone polymers, is the class of linearalternating polymers of carbon monoxide and at least one ethylenicallyunsaturated hydrocarbon. This type of polymers is disclosed in EuropeanPatent Applications such as Nos. 121,965; 181,014; 213,671; and 257,663which are herein incorporated by reference. Additionally, this class ofpolymers is disclosed in numerous U.S. patents assigned to Shell OilCompany, exemplified by U.S. Pat. Nos. 4,880,865 and 4,822,871 which areherein incorporated by reference.

Polyketone polymers have relatively high molecular weights and are usedin the production of shaped articles, such as containers for food anddrink and parts for the automotive industry, which are produced byprocessing the polyketone polymer according to well known methods.

It is known that polyketone polymers have stability problems. See forexample R. Gooden, et al, Journal of Polymer Science: Part A: PolymerChemistry, Vol. 24, 3191-3199 (1986) and R. Gooden, et al., New Trendsin the Photochemistry of Polymers, Applied Science p. 159 (1985).

These stability problems include ultraviolet (UV), melt stability, andheat aging stability, sometimes also referred to as continuous usetemperature (CUT). While antioxidants and other additives provide somedegree of improvement, it would be of advantage to provide newtechniques and materials which yield further improvements in thermaloxidative stability of linear alternating polymers of carbon monoxideand at least one ethylenically unsaturated hydrocarbon. For mostpolymers including polyketones, thermal oxidative degradation leads tochain scission, reduction in molecular weight, and loss of physicalproperties. These adverse effects of oxidative chain scission reactionsare undesirable, and continue to present a problem to those of skill inthe art. Thus, there continues to exist the need to produce ethylene-COpolymers that have and exhibit superior melt stability properties.

It is a discovery of this invention that addition of magnesium oxide andalumina to a polyketone polymer composition result in an improvement inthe melt stability of the composition.

SUMMARY OF THE INVENTION

It is a general object of this invention to provide a stabilizedpolyketone blend.

It is a particular object of this invention to produce a melt stabilizedpolyketone blend.

It is a further object of this invention to provide a stabilizedpolyketone blend having a good balance of properties.

In accordance with this invention, it is now provided a melt stabilizedpolyketone blend, comprising a major portion of a linear alternatingpolymer of carbon monoxide and at least one ethylenically unsaturatedhydrocarbon, and a minor portion of magnesium oxide and alumina in anamount sufficient to function as a melt stabilizer.

DETAILED DESCRIPTION OF THE INVENTION

The materials useful in practicing this invention include a linearalternating polymer of carbon monoxide and at least one ethylenicallyunsaturated hydrocarbon (simply referred to as a polyketone polymer),and a melt stabilizing agent comprising of magnesium oxide and alumina.In general, the practice of this invention involves suitably admixingsuitable quantities of the useful materials to form a melt stabilizedpolyketone polymer composition.

During melt processing, the neat polyketone polymer exhibits anundesirable viscosity increase. It is most desirable for a thermoplasticpolymer to have little or no viscosity increase during processing. Mostcommercial-grade engineering thermoplastics exhibit little or no changein viscosity during melt processing because of the presence of anadditive package selected to minimize such a change in properties. Thisinvention stabilizes the polyketone polymers so that they remainunchanged upon being subjected to conditions which would otherwise bringabout a change in their properties. This object is accomplished byadmixing the inventive stabilizing agent with the polyketone polymer.

The inventive stabilizing agent generally contains a mixture ofmagnesium oxide and alumina preferably prepared by the methodsubsequently disclosed herein. The addition of the stabilizing agent tothe polyketone polymer results in an improved melt stabilizedcomposition. This improvement in melt stability is evidenced by arelatively constant apparent crystallinity when subjected to meltprocessing operations of melting and solidification (crystallization).This improvement in retained apparent crystallinity offers considerableadvantages which are not to be found when unstabilized polymers areutilized. For example, the stabilized composition is often formed asnibs by passage through an extruder. The nibs are then injection moldedto produce a shaped article, in each case without substantial decreasein crystallinity as determined by a relatively constant melting point orother related physical property. The compositions of the invention areparticularly useful in this and other applications which require aseries of melting and solidification cycles. While the compositions ofthe invention are usefully processed by conventional techniques which donot involve melting and solidification of the polymer the advantages ofthe stabilized compositions are most apparent when melt processingoperations are to be employed. Thus, the compositions of the inventionare useful in a variety of applications as engineering thermoplasticsbut are particularly useful in the production of shaped articlesrequiring a number of melting/solidification cycles. Illustrative ofsuch articles are containers for food and drink and parts and housingsfor automotive applications.

The polymer of the invention, the inventive stabilizing agent,conventional agents typically useful in the formulation of the inventivecomposition, and a process for producing the stabilized polyketonepolymer of the invention are discussed in more details in varioussections of this specification.

THE POLYMER

The polyketone polymers which are employed as the major component of themelt stabilized polymer composition of the invention are of a linearalternating structure and contain substantially one molecule of carbonmonoxide for each molecule of unsaturated hydrocarbon. Suitableethylenically unsaturated hydrocarbons for use as precursors of thepolyketone polymers have up to 20 carbon atoms inclusive, preferably upto 10 carbon atoms, and are aliphatic such as ethylene and otherα-olefins including propylene, 1-butene, isobutylene, 1-hexene, 1-octeneand 1-dodecene, or are arylaliphatic containing an aryl substituent onan otherwise aliphatic molecule, particularly an aryl substituent on acarbon atom of the ethylenic unsaturation. Illustrative of this latterclass of ethylenically unsaturated hydrocarbons are styrene,p-methylstyrene, p-ethylstyrene and m-isopropylstyrene. The preferredpolyketone polymers are copolymers of carbon monoxide and ethylene orterpolymers of carbon monoxide, ethylene and a second ethylenicallyunsaturated hydrocarbon of at least 3 carbon atoms, particularly anα-olefin such as propylene.

When the preferred polyketone terpolymers are employed as the majorpolymeric component of the blends of the invention, there will be withinthe terpolymer at least about 2 units incorporating a moiety of ethylenefor each unit incorporating a moiety of the second hydrocarbon.Preferably, there will be from about 10 units to about 100 unitsincorporating a moiety of the second hydrocarbon. The polymer chain ofthe preferred polyketone polymers is therefore represented by therepeating formula

    --CO--CH.sub.2 --CH.sub.2)].sub.x [CO--G)].sub.y

wherein G is the moiety of ethylenically unsaturated hydrocarbon of atleast 3 carbon atoms polymerized through the ethylenic unsaturation andthe ratio of y:x is no more than about 0.5. When copolymers of carbonmonoxide and ethylene are employed in the compositions of the invention,there will be no second hydrocarbon present and the copolymers arerepresented by the above formula wherein y is zero. When y is other thanzero, i.e., terpolymers are employed, the --CO--CH₂ CH₂ -- units and the--CO--G-- units are found randomly throughout the polymer chain, andpreferred ratios of y:x are from about 0.01 to about 0.1. The end groupsor "caps" of the polymer chain will depend upon what materials werepresent during the production of the polymer and whether or how thepolymer was purified. The precise nature of the end groups does notappear to influence the properties of the polymer to any considerableextent so that the polymers are fairly represented by the formula forthe polymer chain as depicted above.

Of particular interest are the polyketone polymers of number averagemolecular weight from about 1000 to about 200,000, particularly those ofnumber average molecular weight from about 20,000 to about 90,000 asdetermined by gel permeation chromatography. The physical properties ofthe polymer will depend in part upon the molecular weight, whether thepolymer is a copolymer or a terpolymer and, in the case of terpolymers,the nature of the proportion of the second hydrocarbon present. Typicalmelting points for the polymers are from about 175° C. to about 300° C.,more typically from about 210° C. to about 270° C. The polymers have alimiting viscosity number (LVN), measured in m-cresol at 60° C. in astandard capillary viscosity measuring device, from about 0.5 dl/g toabout 10 dl/g, more frequently from about 0.8 dl/g to about 4 dl/g.

A preferred method for the production of the polyketone polymers isillustrated by U.S. Pat. No. 4,843,144 (Van Broekhoven et al.). Thecarbon monoxide and hydrocarbon monomer(s) are contacted underpolymerization conditions in the presence of a catalyst compositionformed from a compound of palladium, the anion of a non-hydrohalogenicacid having a pKa (measured in water at 18° C.) of below about 6,preferably below 2, and a bidentate ligand of phosphorus. The scope ofthe polymerization is extensive but, without wishing to be limited, apreferred palladium compound is a palladium carboxylate, particularlypalladium acetate, a preferred anion is the anion of trifluoroaceticacid or p-toluenesulfonic acid and a preferred bidentate ligand ofphosphorus is 1,3-bis(diphenylphosphino)propane or1,3-bis[di(2-methoxyphenyl)phosphino]propane.

The polymerization to produce the polyketone polymer is conducted in aninert reaction diluent, preferably an alkanolic diluent, and methanol ispreferred. The reactants, catalyst composition and reaction diluent arecontacted by conventional methods such as shaking, stirring or refluxingin a suitable reaction vessel. Typical polymerization conditions includea reaction temperature from about 20° C. to about 150° C., preferablyfrom about 50° C. to about 135° C. The reaction pressure is suitablyfrom about 1 atomosphere to about 200 atmospheres but pressures fromabout 10 atmospheres to about 100 atmospheres are preferred. Subsequentto polymerization, the reaction is terminated as by cooling the reactorand contents and releasing the pressure. The polyketone polymer istypically obtained as a product substantially insoluble in the reactiondiluent and the product is recovered by conventional methods such asfiltration or decantation. The polyketone polymer is used as recoveredor the polymer is purified as by contact with a solvent or extractionagent which is selective for catalyst residues.

MELT STABILIZING AGENT

The melt stabilizing agent comprises a mixture of magnesium oxide andalumina prepared in the manner disclosed herein.

PREPARATION OF MAGNESIUM HYDROXIDE

A stirred solution of 100 g (492 m mole) of magnesium chloridehexahydrate (Aldrich, A. C. S. reagent) in 300 ml of deionized water wastreated, dropwise, over a 15 min. period with 28% ammonium hydroxide toa final pH of 9.6. The resulting suspension was stirred for anadditional 1.5 hr. and then filtered to collect the precipitated solids.

The solids were washed with deionized water until no chloride wasdetected in the filtrates (by testing with silver nitrate solution) andthen dried in the vacuum oven for 16 hr. at 110° C. under a slow streamof nitrogen.

PREPARATION OF ALUMINA

To a 1 liter Erlenmeyer flask was added 125 g (333 mmole) of aluminumnitrate nonanhydrate (Mallinkrodt, R. A.) and 500 ml of deionized water.The mixture was stirred at room temperature to give a homogeneoussolution.

In a separate 2 liter Erlenmeyer flask was prepared a 1 molar solutionof ammonium carbonate by dissolving 193 g (2 mole) of ammonium carbonate(Aldrich, A. C. S. reagent) in deionized water and diluting to a volumeof 2 liters.

The nitrate solution and the ammonium carbonate solution were pumped,over a 20 minute period, simultaneously (via 2 masterflex pulse pumps)into a 6 liter stainless steel beaker containing 1.5 liter of deionizedwater which was stirred with a mechanical stirrer and heated at 50° C.The reaction temperature was maintained at 50° C. and the pH at 7.5 byadjusting the flow rate of the ammonium carbonate solution during theaddition and then the reaction mixture was stirred for an additional 2hr. at 50° C., after all of the nitrate solution had been added.

The precipitated alumina was collected by vacuum filtration and washedby resuspending it in 1 liter of fresh deionized water and refiltering20 times to give a final conductance of 65 us/cm of the filtrate asmeasured by a conductance meter. The solids were then dried for 16 hr.at 110° C. in the vacuum oven under a slow stream of nitrogen to givethe freshly prepared alumina.

PREPARATION OF MgO-Al₂ O₃

A mixture of 0.75 g (12.9 mmole) of freshly prepared magnesiumhydroxide, 2.25 g (22 mmole) of freshly prepared alumina and a few dropsof deionized water were combined in a mortar. The mixture was kneadedtogether over a 2 hr. period to make a thick paste and then dried in thevacuum oven at 110° C. under a slow stream of nitrogen for 16 hr. toyield 2.8 g of dried solids.

The dried solids were calcined over a 5 hr. period to 500° C. with 100°C./hr. increases in temperature to give 1.6 g of product. Analysis byplasma emission found: Al, 35.0 wt %; Mg, 18.0 wt %; Na, 290 ppm. Theweight ratio of Mg/Al was 1/1.94 and the weight ratio of MgO/Al₂ O₃ was1/0.88.

By varying the ratio of alumina to magnesium hydroxide, differentcompositions of MgO/Al₂ O₃ can be obtained. [J. Catal., 47, 358(1977)]

OTHER ADDITIVES

The melt stabilized polymer composition of the invention may alsoinclude other additives such as antioxidants, dyes, other fillers orreinforcing agents, fire resistant materials, mold release agents,colorants and other materials designed to improve the processability ofthe polymers or the properties of the resulting compound. Such additivesare added prior to, together with, or subsequent to the blending of thepolyketone and the melt stabilizing agent.

AMOUNTS AND PROCESS

The melt stabilized polymer composition of this invention comprises amajor amount of the linear alternating polymer of carbon monoxide and atleast one ethylenically unsaturated hydrocarbon and a lesser amount ofthe melt stabilizing agent. Generally speaking, at least up to oneweight percent (1 wt %) of the melt stabilizing agent is desired. Thisquantity of melt stabilizing agent can be made up from variouspermutations magnesium oxide and alumina previously disclosed. Forexample, 0.75 wt % magnesium oxide and 0.25 wt % alumina, or 0.50 wt %of each of these oxides may be used.

The method of producing the melt stabilized polymer composition of thisinvention is not critical so long as a relatively uniform distributionof the melt stabilizer throughout the polyketone is obtained.Conventional mixing devices and/or procedures known in the art aresuitable for admixing the components of this invention.

The following examples and table further illustrates the various aspectsof the invention.

EXAMPLE 1 Preparation of Polymer

A linear alternating terpolymer of carbon monoxide, ethylene, andpropylene was produced in the presence of a catalyst composition formedfrom palladium acetate, trifluoroacetic acid and1,3-bis[di(2-methoxyphenyl)phosphino]propane. The polyketone polymer hada melting point of about 223° C. and an LVN of about 1.1 dl/g whenmeasured in m-cresol at 60° C.

EXAMPLE 2 Preparation of Inventive Samples and Testing of ViscosityProperties of Samples

A portion of the polymer of Example 1 was ground to 60 mesh, and thenpowder-mixed with magnesium oxide-alumina compositions in a Henschelmixer for 5 minutes. Polymer samples containing magnesium oxide andalumina in various ratios of the two components were prepared, as shownin Table I. The samples were compounded in a 3/4 inch Braebender singlescrew extruder, operating at 60 to 100 rpm with melt temperature between230° and 250° C. The viscosity of each sample was determined over timein the melt in a Rheometrics parallel plate rheometer operated at 275°C. Table I lists the initial melt viscosity and the viscosity after 10and 28 minutes. During commercial processing, polymers are typically ina melt phase for less than 10 minutes.

                  TABLE I                                                         ______________________________________                                                                        Viscosity                                     MgO   Al.sub.2 O.sub.3                                                                      Total             (Pa-sec)                                      (wt %)                                                                              (wt %)  MgO + Al.sub.2 O.sub.3                                                                    0 min.                                                                              10 min. 28 min.                               ______________________________________                                        0     0       0           990   8,341   24,960                                .1    .90     1           990   4,823   14,450                                .25   .75     1           990   4,417   12,990                                .5    .5      1           990   4,290   13,670                                ______________________________________                                    

The results of Table I demonstrate that the magnesium oxide-aluminacomposition is an effective agent for decreasing the viscosity increaseof the polyketone polymer melt. With the magnesium oxide-aluminastabilizers incorporated, the viscosity of the samples after 10 minutesand 28 minutes of heating is always less than that of samples withoutthese stabilizers.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

That which is claimed is:
 1. A melt stabilized polymer compositioncomprising:(a) a linear alternating polymer of carbon monoxide and atleast one ethylenically unsaturated hydrocarbon; and (b) a mixture ofmagnesium oxide and alumina in an amount sufficient to function as amelt stabilizer.
 2. A composition as in claim 1 wherein the linearalternating polymer is represented by the repeating formula

    --CO--CH.sub.2 --CH.sub.2)].sub.x [CO--G)].sub.y


3. A composition as in claim 1 wherein the mixture of magnesium oxideand alumina is present in an amount of from about 0.01 up to about 1 wt%.
 4. A composition as in claim 1 wherein said magnesium oxide andalumina are present in an amount of about 0.1 wt % and 0.9 wt %respectively.
 5. A composition as in claim 1 wherein magnesium oxide andalumina are present in an amount of about 0.25 wt % and 0.75 wt %respectively.
 6. A composition as in claim 1 wherein magnesium oxide andalumina are each present in an amount of about 0.5 wt %.
 7. Acomposition as in claim 1 wherein the weight ratio of magnesiumoxide:alumina is from about 1:0.2 to about 0.88.
 8. A melt stabilizedpolymer composition comprising:(a) a linear alternating polymer ofcarbon monoxide and at least one ethylenically unsaturated hydrocarbon;and (b) 0.5 wt % each of magnesium oxide and alumina.
 9. A shapedarticle of manufacture produced from the composition of claim
 1. 10. Acomposition as in claim 3 wherein said mixture of magnesium oxide andalumina is present in an amount of from about 0.1 to 1 wt %.
 11. Acomposition as in claim 3 wherein said mixture of magnesium oxide andalumina is present in an amount of from about 0.5 to 1 wt %.
 12. Acomposition as in claim 1 wherein said polymer is a terpolymer of carbonmonoxide, ethylene, and a second ethylenically unsaturated hydrocarbon.13. A composition as in claim 12 wherein said second ethylenicallyunsaturated hydrocarbon is propylene.